Water is a commonly used food plasticizer, which to a great extent determines the texture and softness of various food products. However, water is easily lost to the environment either by evaporation or by migration from areas of high water activity to areas of low water activity within the food product during storage of the product. The result of such evaporation or migration of water is that the texture, appearance or flavour of the food product may be altered during storage. In order to overcome this problem, other plasticizers such as polyols are commonly used. These plasticizers are advantageous to use because they do not easily migrate between areas of high and low water activity, they do not support microbial growth and they do not evaporate in the environment during prolonged storage periods. The longer the desired shelf life of the food product, the higher the amount of plasticizer that needs to be added to counteract the hardening of the food product due to water loss.
In several cases, however, the maximum amount of plasticizer added to the food product is limited by processing requirements. For example, in cases of food products which are deposited, molded or extruded the process requires that the food product is hard enough to maintain its shape during forming and subsequent processing. This is particularly the case with various "composite" food products which consist of various layers or regions of varying composition, texture, and water activity such as filled cereals and baked products, breakfast and nutritional bars, or confectionery products, etc.